Semiconductor package

ABSTRACT

A semiconductor package is comprised of a semiconductor device  4  mounted on a die-pad  3 , a wire  6  for electrically connecting some electrodes of the semiconductor device  4  and terminals  5  of lead frame, wires  8  for bonding the other electrodes of semiconductor device to the surface of die-pad for grounding, molding compound  7  for encapsulating the outer area of semiconductor device  4  under a state where the back face of die-pad  3 , the lower face and side face of terminals  5  are exposed, wherein portions for plated with silver connecting of wires on the surface of the die-pad are formed at points positioned between a peripheral edge of the die-pad and an outer edge of the semiconductor device with leaving spaces from both the edges. The adhesion of die-pad  3  to bonding compound  7  is improved so that no trouble of coming-off of wires occur even if heat is applied to the contact points of die-pad  3  to wires  8  when mounting semiconductor package on a printed circuit board.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a semiconductor package in which a semiconductor device is mounted on a lead frame and the outside thereof, particularly the upper surface of semiconductor device is encapsulated with molding compound.

[0003] 2. Description of the Prior Art

[0004] In recent years, it has been required to miniaturize and shape semiconductor product mounted on a substrate thinner, as packaging of semiconductor is made denser. It has been severely required for LSI to reduce the number of chips by improving integration level and to miniaturize and make a package lighter. The popularization of so-called CSP (Chip Size Package) is rapidly advancing. Particularly, in the development of thin semiconductor product with lead frame, the semiconductor package of single side encapsulation type has been developed in which a semiconductor device is mounted on a lead frame and the surface of semiconductor device mounted on a lead frame is encapsulated with molding compound.

[0005]FIG. 1 is a sectional view of one example of semiconductor package. FIG. 2 is a plan view thereof seen through molding compound. The semiconductor package shown in FIGS. 1 and 2 is comprised of a lead frame 1, a semiconductor device 4 mounted on die-pad 3 supported with suspending leads 2 of lead frame 1, metallic thin wires 6 electrically connecting electrodes provided on the top face of the semiconductor device 4 with terminals 5 of lead frame 1, respectively and molding compound 7 for encapsulating the outside region of semiconductor device 4 including the upper side of semiconductor device 4 and the lower side of die-pad 3. The semiconductor package is of so-called non-lead type in which outer leads are not projected from the semiconductor package and the two of inner leads and outer leads are integrated into terminals 5, wherein in used lead flame 1, suspending leads 2 are directed upward in such a manner that die-pad 3 is positioned higher than terminals 5. Since such a step is provided between die pads 3 and terminals 5, molding compound 7 can be inserted into the lower side of die-pad 3.

[0006] Since semiconductor device is miniature, a matrix type frame is mainly used for the above-mentioned non-lead type of semiconductor package, in which plural semiconductor devices are arranged in a direction of a width of the matrix type frame. Further, recently, from a demand for cost down, it is thought to switch over a frame of individually molding type shown in FIG. 3 to a frame of collectively molding type shown in FIG. 4.

[0007] In the frame of individually molding type, as shown in FIG. 3(A), individual molding cavities C of small size are provided separately within a frame F. After molding, individual semiconductor packages are stamped out so that semiconductor packages S shown in FIG. 3(B) are obtained. Namely, semiconductor devices are mounted on die-pads of lead frames through silver paste and others, and wire bonding is carried out. Thereafter, respective semiconductor devices are individually molded with molding compound and the molded semiconductor devices are stamped out to form individual semiconductor packages.

[0008] In the frame of collectively molding type, as shown in FIG. 4(A), some molding cavities C of large size are provided within a frame F. Multiple semiconductor devices are arranged in matrix within each molding cavity C, respectively and collectively molded with molding compound. Thereafter, the collectively molded semiconductor devices are cut at grid-leads L by means of dicing saw so that a semiconductor package S shown in FIG. 4(B) is obtained. Namely, semiconductor devices are mounted on die-pads of lead frames through silver pastes and others and wire bonding is carried out. Thereafter, plural semiconductor devices arranged are collectively molded with molding compound to a given cavity size, and then the collectively molded semiconductor devices are cut to form individual semiconductor packages by dicing.

[0009] In the above-mentioned non-lead semiconductor package, there is a type of semiconductor package in which a die-pad is exposed to increase the effect of heat radiation and bonding of some electrodes of semiconductor device to the surface of die-pad 3 for grounding is needed. FIG. 5 is a sectional view of such a type of semiconductor package. FIG. 6 is a plan view of the semiconductor package seen through molding compound thereof. When producing the collectively molding semiconductor packages, each semiconductor device 4 is mounted on die-pad 3 of lead frame 1 through silver past and others. Thereafter, given electrodes on the top face of each semiconductor device 4 are connected with terminals through wires 6, and the other electrodes on each semiconductor device 4 are connected with the surface of die-pad 3 through wire 8. Thereafter, semiconductor devices are correctively molded with molding compound 7, and then as above-mentioned, the collectively molded semiconductor devices are cut to form individual semiconductor packages. In this case, in a type of semiconductor package shown in FIG. 1, silver plating (not shown) is made on the wire connecting points of terminals 5 in lead frame 1, while in a type of semiconductor package shown in FIG. 5, silver plating is made also on the surface of die-pad 3.

[0010] When mounting the semiconductor package shown in FIG. 5 on a printed circuit board, solder plating is made not only on the exposed portions of terminals 5, but also on the exposed portions of die-pad 3. Further, solder cream is applied on areas on printed circuit board corresponding to the exposed portions of terminals 5 and die-pad 3. Semiconductor package mounted on a printed circuit board is heated in an oven at about 230° C., by which solder is made re-flow so that semiconductor package is fixed firmly at a given position on a printed circuit board.

[0011] However, in the semiconductor package shown in FIG. 5, stress is applied to the contact point of die-pad 3 to wires 8 when making solder re-flow from a difference in thermal expansion coefficient between molding compound 7 and copper material of lead frame 1, and the adhesion of portions plated silver for connecting of wires applied on the surface of die-pad to molding compound 7 is not enough so that a trouble of coming-off of wires occurs. Further, there is a case where crack is generated in molding compound from neighborhood of corners of die-pad as the starting point, wherein there is the possibility that cutting of wires occurs according to a state of crack.

SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide a semiconductor package in which bonding of some electrodes of semiconductor device to the surface of die-pad for grounding is made, wherein no trouble of coming-off of wires or cutting of wires occurs.

[0013] In order to achieve the above-mentioned object, a semiconductor package of the present invention comprises a semiconductor device mounted on a die-pad supported by suspending leads of a lead frame, wires for electrically connecting given electrodes arranged on a top face of the semiconductor device with terminals of the lead frame, wires for bonding the other electrodes arranged on the top face of the semiconductor device to the surface of the die-pad for grounding and molding compound for encapsulating an outer area of the semiconductor device including all the wires, while the lower face of die-pad and the lower face and side face of terminals are exposed, wherein portion(s) plated with silver for connecting of wires on the surface of the die-pad are formed at points positioned between a peripheral edge of the die-pad and an outer edge of the semiconductor device with leaving spaces from both the edges.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a sectional view of one example of a semiconductor package.

[0015]FIG. 2 is a plan view of the semiconductor package shown in FIG. 1, showing a state thereof seeing through the resin encapsulating the semiconductor package.

[0016]FIG. 3 is an explanatory view of an individually molding type of semiconductor package.

[0017]FIG. 4 is an explanatory view of a collectively molding type of semiconductor package.

[0018]FIG. 5 is a sectional view of semiconductor package wherein some electrodes are bonded to a die-pad through wires for grounding.

[0019]FIG. 6 is a plan view of the semiconductor package shown in FIG. 5, showing a state thereof seen through molding compound.

[0020]FIG. 7 is a sectional view of one example of semiconductor package according to the present invention.

[0021]FIG. 8 is a plan view of the semiconductor package shown in FIG. 7, showing a state thereof seen through molding compound.

[0022]FIG. 9 is a sectional view of another example of semiconductor package according to the present invention.

[0023]FIG. 10 is a sectional view of the semiconductor package shown in FIG. 9, showing a state thereof seen through molding compound.

[0024]FIG. 11 is a sectional view of further example of semiconductor package according to the present invention.

[0025]FIG. 12 is a plan view of the semiconductor package shown in FIG. 11, showing a state thereof seen through molding compound.

[0026]FIG. 13 is a sectional view taken on line A-A of FIG. 12.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027] Then, referring to figures, embodiments of the present invention are explained.

[0028]FIG. 7 is a sectional view of one example of semiconductor package according to the present invention. FIG. 8 is a plan view showing a state of the semiconductor package seen through molding compound.

[0029] The semiconductor package is a collectively molding type of semiconductor package as shown in FIGS. 7 and 8. Referring to FIGS. 7 and 8, the semiconductor package comprises a semiconductor device 4 mounted on a die-pad 3 supported by suspending leads 2 of a lead frame 1, wires 6 for electrically connecting given electrodes 9 arranged on a top face of the semiconductor device 4 with terminals 5 of the lead frame, wires 8 for bonding the other electrodes 10 arranged on the top face of semiconductor device 4 to the surface of the die-pad for grounding and molding compound 7 for encapsulating an outer area of semiconductor device 4 including all the wires 6, 8, while the lower face of die-pad 3 and the lower face and side face of terminals 5 are exposed. Further, portions 11 plated with silver are formed in wire-connection parts of terminals 5, and portion 12 plated with silver for connecting of wires is formed on the surface of die-pad 3. Portions 11, 12 plated with silver are shown with hatching in FIG. 8 in order to make easy to read the figure.

[0030] Portion 12 plated with silver on the surface of die-pad 3 is, as shown in FIG. 8, formed into a shape of line between a peripheral edge of die-pad 3 and an outer edge of semiconductor device 4 with leaving spaces from both the edges. Accordingly, molding compound 7 is made into contact not only with portion 12 plated with silver but also with copper material of lead frame on both sides of the linear shaped area plated with silver. Therefore, adhesion of portion plated with silver to molding compound 7 is improved as compared with a case where all molding compound 7 is made into contact with portion plated with silver.

[0031] Further, in the example shown in FIGS. 7 and 8, portion 12 plated with silver is formed continuously. However, portion 12 plated with silver may be divided into a plurality of portions plated with silver formed into a form of islands only to parts of die-pad 3 to be connected with wire 8. The discontinuous forming of portions 12 plated with silver in such a manner makes an area of resin 7 made into contact with copper surface of lead frame larger so that the adhesion of resin 7 to portions 12 plated with silver is improved.

[0032] In this case, portions 11, 12 plated with silver are formed on a frame in which a plurality of lead frames 1 are arranged in matrix, in the same manner as conventional case, wherein however, portions 12 plated with silver on die-pad 3 are formed into a linear shape or discontinuously, differently from conventional case.

[0033]FIG. 9 is a sectional view of another example of semiconductor package according to the present invention. FIG. 10 is a plan view of the semiconductor package, showing a state thereof seen through molding compound.

[0034] The semiconductor package is nearly the same as the example shown in FIGS. 7 and 8, wherein however, this semiconductor package has concave portions 13, 14 formed along both sides of portion 12 plated with silver for connecting of wires on the surface of die-pad 3. Since molding compound 7 is inserted into the concave portions 13, 14 in this semiconductor package, the adhesion of molding compound 7 to die-pad 3 is further improved.

[0035] In this case, there is an effect that the adhesion of molding compound 7 to die-pad 3 can be increased even by only a concave portion formed on one side of linear portion 12 plated with silver. Further, in order to increase the adhesion of molding compound 7 to die-pad 3, the concave portion can be formed into through hole. However, in this case, it is needed to leave a part of concave portion in such a manner that die-pad 3 does not fall down.

[0036]FIG. 11 is a sectional view of further example of semiconductor package according to the present invention. FIG. 12 is a plan view showing a state of the semiconductor package seen through molding compound. FIG. 13 is a sectional view taken on line A-A of FIG. 12.

[0037] The semiconductor package shown in FIG. 11 differs from the first example shown in FIGS. 7 and 8 in the structure of the portion 12 plated with silver for connection of wires on the surface of die-pad 3. That is, portions plated with silver for connection of wires are formed discontinuously. And concave portions 15 are formed between discontinuous portions 12 plated with silver. In the semiconductor package, since molding compound 7 penetrates into these concave portions 15, the adhesion of molding compound 7 to die-pad 3 is further increased.

[0038] In this case, through hole(s) can be applied instead of concave portions 15, by which the adhesion of molding compound 7 to die-pad 3 can be increased.

[0039] In this case, the above-mentioned concave portions can be formed by half-cutting by etching or impressing of material of lead frame, when forming a lead frame. Further, through holes can be formed by etching material of lead frame from both sides of the material or stamping the material.

[0040] In the-above-mentioned explanation, a collectively molding type of semiconductor package is mentioned. An individually molding type of semiconductor package has the same construction as the collectively molding type of semiconductor package.

[0041] As explained hereinbefore, the semiconductor package of the present invention comprises a semiconductor device mounted on a die-pad supported by suspending leads of a lead frame, wires for electrically connecting given electrodes arranged on a top face of the semiconductor device with terminals of the semiconductor device, wires for bonding the other electrodes arranged on the top face of the semiconductor device to the surface of the die-pad for grounding and molding compound with which an outer area of the semiconductor device including all the wires is encapsulated, wherein portions plated with silver for connecting of wires on the surface of the die-pad are formed at points positioned between a peripheral edge of the die-pad and an outer edge of the semiconductor device with leaving spaces from both the edges. Accordingly, molding compound is also made into contact with copper material of lead frame so that the adhesion of die-pad to molding compound is increased. Therefore, the reliability can be secured that no trouble of coming-off of wires or cutting of wires occur in mounting a semiconductor package on a printed circuit board. 

What is claimed is:
 1. A semiconductor package comprising a semiconductor device mounted on a die-pad supported by suspending leads of a lead frame, wires for electrically connecting given electrodes arranged on a top face of the semiconductor device with terminals of the lead frame, wires for bonding the other electrodes arranged on the top face of the semiconductor device to the surface of the die-pad for grounding and molding compound with which an outer area of the semiconductor device including all the wires is encapsulated, wherein portion(s) plated with silver for connecting of wires on the surface of the die-pad are formed at points positioned between a peripheral edge of the die-pad and an outer edge of the semiconductor device with leaving spaces from both the edges.
 2. A semiconductor package as claimed in claim 1, wherein the portion plated with silver for connecting of wires on the surface of the die-pads is formed into a shape of line.
 3. A semiconductor device as claimed in claim 1, wherein the portion plated with silver for connecting of wires on the surface of the die-pad is formed into a shape of line and at least a concave portion is formed along one side of the linear shaped area plated with silver.
 4. A semiconductor device as claimed in claim 1, wherein the concave portion is provided with through hole(s) formed leaving at least a part of the concave portion.
 5. A semiconductor device as claimed in claim 1, wherein the portions plated with silver for connecting of wires on the surface of the die-pad are formed discontinuously.
 6. A semiconductor device as claimed in claim 5, wherein concave portions are formed between the discontinuous portions plated with silver.
 7. A semiconductor device as claimed in claim 1, wherein through holes are formed between the discontinuous portions plated with silver. 